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grey water reuse as a sustainable alternative resouree
Grey Water Reuse As A Sustainable Alternative Water Resource 1 _______________________________________________________________________________ CAFEO 28 Grey Water Reuse As A Sustainable Alternative Water Resource Ir. Ellias Saidin 1 , Dr Aminuddin Baki 2 , Dr Ismail Atan 2 1. Perunding Ikatan, Petaling Jaya, Selangor 2. Dept of Civil Engineering, UiTM, Shah Alam, Selangor ABSTRACT Grey water is the discharge from laundry, baths and dishwashers which constitutes about 50-80% of wastewater from a household discharge. This water is suitable for reuse in subsurface irrigation without treatment and/or for toilet flushing after some simple treatment. In parts of the world, guidelines are produced and grey water reuse is permitted by local authorities amidst concern over the potential health hazard of the practice. In Australia, where water resource is limited, grey water is the second source of water in 55% of households; with 25% of households reporting collecting their laundry water for reuse, 19% from bathrooms and 13% from the kitchen. In Malaysia typical savings of about 37% of water consumption in a household may be realized. The safe reuse of grey water is restricted and confined to the landscape and general cleaning within the home where it was generated. For gardening, the water has to be dispersed by drip irrigation, directly into the ground within twenty-four hours. Laundry water for general cleaning and flushing must be generated from washing of non-soiled clothes only. With the practice of grey water reuse, demand from public water supply will be reduced and in water stressed areas, water resource will become more sustainable. There will be less impact on the stream and watercourses as discharge are reduced as the resource is reused at the generating source. Keywords: greywater, graywater, water reuse, water conservation, water sustainability, water recycle, water management, alternative water resource. 1.0 INTRODUCTION Sewage generated in a household may be separated into greywater and blackwater discharges. Greywater is commonly defined as the wastewater discharged from laundry/washing, baths, hand basins and (cleaned) dishwashing machines and excludes discharges from kitchen, toilets, urinal and bidet. (NSW Guidelines, 2008) The term grey water is used as the wastewater generated is cloudy and the color is contrasted to white water (clear freshwater) and black water (soiled wastewater from sewage). The water contains nutrients from detergents, soaps and organic matter which are suitable for irrigation of grass, plants and selective vegetables. The WHO recognise that the utilisation of greywater contributes to less pressure on water resource, reduces health risks of downstream communities, helps to improve environmental health and reduces environmental impacts downstream.(WHO Guidelines 2006). In developed communities, the reuse of greywater is part of the practice of Integrated Water Management practices which will result in water conservation and reduce impact on the water environment downstream such as flooding, erosion, water quality as well as reducing costs of providing urban drainage infrastructure. Presently, many local authorities and health department in various countries have given due recognition to the reuse of greywater within the households. Installation of Grey Water Reuse As A Sustainable Alternative Water Resource 2 _______________________________________________________________________________ CAFEO 28 a greywater system can be carried out in homes by complying with Guidelines and Regulations issued by the authorities for the safe utilisation of this water resource. In Europe, Australian and USA where the International Plumbing Code is adopted, grey water from showers, bathtubs and hands basin can be used for toilet flushing leading to over 30% of a domestic demand. (Chap 13, International Plumbing Code). The City of Malibu, California passed laws in 1994 on the standards for greywater systems for installation in homes. However it was also reported that in 1992, 8% of beachfront home and 33% of inland homes were already using some form of greywater systems. In 2001, The Arizona Department of Environmental Quality issues guidelines and permits the use of graywater within a residential property generating less than 400gallons per day, for subsurface irrigation within the premises. The water table has to be a minimum 5 ft blow ground, and discharged at 4 feet away from building foundations, and the soil has to be sufficiently permeable without percolation on the surface. (Val L Little, 2001). The States in Australia have regularly updated their Guidelines for the installation of greywater systems in the home to be carried out by licensed plumbers and have issued certificate of approvals for greywater systems. Grants are offered to Australian homes installed with greywater systems. The government of Cyprus offer subsidies of up to €1700 for the use of greywater in a home. In Tokyo, greywater is mandatory for buildings >30,000 m2 or with potential non-potable demand of more than 100m3/day. (Environment Agency, 2008). Health safety concerns on the reuse of greywater within the home are minimal as pathogens are usually killed after being placed in the soil. Pathogens are not spread to others as atmospheric spraying is not permitted as it generates droplets or aerosols for transport to neighbours. Family members are not at high risks even if in contact with these water borne pathogens as there are body contacts and other means of contacts for pathogens to cross contaminate within the home. An agricultural concern is the high concentration of salts especially sodium in detergents which inhibit seed germination and breaks down the clay molecules in soil. Japanese Cascading Toilet Bowl 2.0 THE QUALITY OF GREY WATER The NSW Guidelines conveniently identifies two greywater streams; bathroom greywater and laundry greywater. The bathroom greywater contains soaps but of very low concentrations that makes the moisture easier to move around the soil particles. The dead skin cells and little body wastes from sweat and other organs contains nitrates and minerals which are highly nutritious for the plants. Grey Water Reuse As A Sustainable Alternative Water Resource 3 _______________________________________________________________________________ CAFEO 28 The laundry greywater is more contaminated with faecal pathogens from soiled clothing than the bathroom source, though laundry water is easier to capture and use. Laundry water contains phosphates and human organic matter for healthy plant growth. The quality or greywater is highly dependent on the detergents, soaps and household practices. A typical composition of greywater from a Western Australia home is reproduced below from West Australia Water Corporation Draft Guidelines 2002. 3.0 HOUSEHOLD GREYWATER QUANTITY The quantity of greywater available for reuse in a household may be estimated from the daily household consumption. The consumption for a typical home in WA, Australia and Malaysia are shown below. Source: Western Australia Water Corporation (2002) Source: Bulletin JKR & Alam Sekitar (2006) Grey Water Reuse As A Sustainable Alternative Water Resource 4 _______________________________________________________________________________ CAFEO 28 The figures indicated that 29% (WA) and 46 %( Malaysia) of the household consumption may be safely reused without treatment with up to 40% and 70% respectively available for reuse after basic treatment. It is noted that in WA where garden watering constitutes 47% of daily water demand, the reuse of greywater is most encouraging to conserve water demand in the home. 4.0 GREY WATER REUSE SYSTEMS A greywater System may be varied in complexity from the direct reuse systems with no treatment, basic physical and chemical treatment and the more complex biological and bio-mechanical treatments systems which will allow for longer storage periods. The more complex systems are applicable in a high consumption and large population condition and have been reported in the UK to be quite unreliable in terms of performance such as odour and water quality.( UK, Environment Agency; 2008) In a household in Australia, the NSW Government permits the reuse of household greywater in three categories. The first category is where the untreated greywater is diverted through pipes to be used in lawn subsurface irrigation within the premises. The second method is where the greywater is partially treated to be reused in toilet flushing, laundry washing and open irrigation. The third category is where the greywater is manually carried in buckets. (NSW Guidelines 2008). The components of a Greywater Reuse System are the Source, Piping and Conveyance, Surge/Balancing Tanks, Filters, Pump and delivery piping system. A separate sanitary plumbing system has to be installed to separate the grey water from the wastewater discharges in a home. Some allowance for treatment by chlorination may be necessary where the water has fouled up. Components in a Greywater Drip Irrigation System Source: http://www.platypusenviro.com.au The amount of water to be used shall be balanced against the demand requirements of the lawn, vegetables or other user demand. The surge tank should not store the greywater for more than 24 hours to avoid odour and microbial problems unless Grey Water Reuse As A Sustainable Alternative Water Resource 5 _______________________________________________________________________________ CAFEO 28 chemical and/or microbial treatment is provided. The pumping flow rate needs to be matched with the infiltration capacity of the soil with the water being preferably fed through subsurface drip piping systems which feed directly the roots of the plant. The water shall not be sprayed or otherwise applied so as not to form airborne aerosols. Overflows and bypass systems must be installed for the greywater to overflow into the municipal wastewater system when there is excess or during heavy rains. Under the NSW Code of Practice, 2006; reywater discharges from the laundry and bathroom may be reused through Greywater Diversion Devices (GDDs) without any treatment process. However to reuse kitchen greywater a Greywater Treatment Systems (GTSs) has to be installed before the water can be reuse either for toilet flushing, laundry and surface and/or sub-surface irrigation outdoors. It is better to install the greywater system during construction as retrofitting is costly and with long investment return periods. Although communal systems may be more reliable in terms of matching supply/demand and water quality, however public perception and acceptability has to be overcome. 5.0 STUDIES OF GREYWATER REUSE Texas A&M El Paso Research Center studied the effects of using greywater (laundry water) discharged from a prison (3,500gpd) on vegetable and cotton crop plots in an arid area receiving less than 250mm of rain. The center concluded that graywater was a good alternative source for irrigation and also landscaping. Mature Cotton plants Photo: Texas A&M University The Water Environment Research Foundation, USA carried out a study where it was concluded that there were no apparent long term effects of landscape irrigation using household greywater on landscaping plants; the soil microbes seem to benefit from the nutrients however subsurface irrigation is recommended to reduce pathogenically contamination.(WERF;11/2007)). Young Tomato Plants Photo: Texas A & M University Grey Water Reuse As A Sustainable Alternative Water Resource 6 _______________________________________________________________________________ CAFEO 28 Households in US have reused their greywater by feeding through sandy flowerbeds in indoor sunlit areas as shown below. Household Indoor Greywater Reuse with Sub-Surface Bed Irrigation Source: http://www.greywater.com/samples.htm 6.0 CONCLUSIONS The practice of reuse of greywater has to be driven by government incentives and regulations. The practice will become more economical as the cost of water is ever increasing. The awareness among the public of sustainability practices to conserve resources and save the environment will drive more greywater practices. Greywater reuse within the home addresses the issue of water conservation particularly in water stressed areas and broadly addresses the sustainability of an alternative water resource for the household where the water is utilised at the source generated. The areas of concern in reusing greywater are the potential health threat and the adverse effect on the plants and the soil biochemistry. With good practice being implemented through issued rules and guidelines from the authorities, the above concerns may be mitigated and greywater is reused safely. REFERENCES Art Ludwig (2008), “”Builders Greywater Guide”; Published by Oasis Design Australian Bureau of Statistics, March 2007; California, Department of Water Resource (Jan 1995), “Graywater Guide – Using Graywater in Your Home Landscape”. City of Malibu, Dept of Environment, Building and Safety (1995), “Greywater Handbooks”; prepared by Peter Warshall and Associates. (July 1995) Draft Guidelines for the Reuse of Greywater in Western Australia. Grey Water Reuse As A Sustainable Alternative Water Resource 7 _______________________________________________________________________________ CAFEO 28 Heather Kinkade-Levario, (2007), “Design for Water”; New Society Publishers Metcalf & Eddy / AECOM (2007), “Water Reuse – Issues, Technologies and Applications”; McGraw Hill NSW Government, Department of Water & Energy, “NSW Guidelines for Greywater Reuse in Sewered, Single Household Residential Premises (May 2008)” Texas A&M El Paso Research Center, WE Jan/Feb 2008; http://www.werf.org. UK environment Agency (2008), “Reusing Greywater and Harvesting Rainwater”; www.environment-agency.gov.uk UK Environment Agency (2008). “Greywater: An Information Guide” www.environment-agency.gov.uk . Val L Little, “Graywater Guidelines”; Published by the Water Conservation Alliance of Southern Arizona (Water CASA). Venhuizen David, P.E., “Decentralised Reuse with Subsurface Drip Irrigation Fields: Issues and Opportunities”; www.venhuizen-ww.com Water Environment Research Foundation; “Long Term Effects of Landscape Irrigation Using Household Greywater”. www.werf.org World Health Organisation: “Guidelines of the Safe Use of Wastewater, Excreta and Greywater”; WHO (2006)